On Wednesday, a new study from the Violence Policy Center showed that the rate at which Americans were killed by firearms exceeds the death rate from motor vehicles in 12 states and the District of Columbia.

It’s a striking finding. For me, though, it raises more questions than it answers, and in doing so, the study shows just how difficult it is to have an evidence-based or nuanced debate about firearms.

First, the facts. In the United States, death by firearms increased during the study period, 1999 to 2010. Without adjusting for population growth, intentional firearm related deaths (homicide and suicide) are up almost 12 percent. According to the CDC, motor vehicle deaths declined 38 percent. So far, the data supports the authors’ conclusion.

But why are motor vehicle deaths a good barometer of whether we are doing well or poorly in preventing firearm deaths? That seems totally arbitrary. Why not compare firearms deaths to another public health epidemic— death from prescription drug overdoses, which have doubled since 1999? Since both prescription drugs and a round from a firearm are intended to change how the human body operates, isn’t that arguably a better comparison? Even if it is just equally arbitrary, it’s fair to point out that good policy is not built on arbitrary comparisons.

The study’s authors say that motor vehicle deaths have declined due to effective public safety campaigns, which is probably true, and firearms deaths are up due to ineffective policy. However, if you adjust for population growth, firearm death rates are virtually unchanged—up less than .2 percent.

More importantly, the real story with firearm deaths over this time period is not about firearms and homicide at all, it's about firearms andsuicide. Adjusted for population growth, homicide by firearm is down almost five percent, although this is almost certainly due to better medical care rather than better public policy—likely also a factor in the declining rate of motor vehicle deaths.

What’s driving the increase in firearm deaths? Suicide. And that’s really important. In raw numbers, suicides by firearm are up 14 percent and up 3 percent when adjusting for the growing population.

While the data on the relationship between firearms and homicide is fuzzy, the relationship between firearms and suicide is crystal clear. More guns= more suicides. If there is no gun in the house, people do not find a different way to commit suicide, they just don't commit suicide.

That takes us to the study’s policy proposals, which are about limiting magazine capacity, eliminating assault weapons, and related proposals. While my personal opinion, from reviewing the firearms and violence literature, is that prior research supports these policy proposals, these policy ideas won't solve the suicide problem.

One thing that might: Much more serious gun safety laws, including restrictions on handgun ownership. But since we can't pass gun safety laws supported by 90 percent of the public, these ideas are a non-starter.

Perhaps a more fruitful way to reduce suicide by firearm would be to have a much more nuanced discussion about the relationship between mental health and firearm possession than is currently underway. While there are certainly legitimate civil liberties concerns to be discussed, linking prescriptions for serious depression to gun forfeiture could potentially have a profound effect on the number of suicides.

Unfortunately, unlike depression and suicidal ideation, "nuance" and "firearms" almost never co-occur.